solved #151

src/Shared/HandyControlDemo_Shared/UserControl/Main/AppNotification.xaml

@@ -3,6 +3,8 @@
              xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
              xmlns:hc="https://handyorg.github.io/handycontrol"
              Background="White"
+             BorderThickness="1"
+             BorderBrush="{DynamicResource BorderBrush}"
              Width="320"
              Height="518">
     <hc:SimplePanel>